Worm Breeder's Gazette 12(5): 48 (February 1, 1993)

These abstracts should not be cited in bibliographies. Material contained herein should be treated as personal communication and should be cited as such only with the consent of the author.

sum-1 ,a New Gene Involved in Vulva Formation

Diane Levitan, Iva Greenwald

Department of Molecular Biology, Princeton University, Princeton, NJ

As described in a previous Gazette article (vol. 12, number 2), we have identified suppressors of the multivulva phenotype of the lin-12 (d) allele n950 .At least three of these suppressors appear to define new genes involved in VPC generation, and have additional effects on fertility and the production of adult alae. One suppressor mutation proved to be an allele of lin-11 . Finally, two of these suppressor mutations appear to be alleles of a new gene involved in vulva formation, sum-1 .The two sum-1 alleles we have isolated, ar131 and ar133 ,cause an Egl- phenotype. These alleles are loss-of-function mutations-- ar131 / meDf5 and ar133 / meDf5 are both Egl- and suppress the Muv phenotype of lin-12 ( n950 ).As described previously, sum-1 mutant animals have no significant VPC lineage defects. Furthermore, although all VPCs undergo 2° lineages in both the single mutant lin-12 ( n950 )and the double mutant lin-12 ( n950 ); sum-1 ( ar131 ),pseudovulvae are only formed in the single mutant.

To test whether suppression of pseudovulvae formation by sum-1 is restricted to 2° lineages, we constructed double mutants with mutations in other Muv genes. sum-1 is epistatic to let-60 ( n1046 )and lin-1 ( n1275 ).Again, the VPC lineages in the double mutants look similar to the VPC lineages of the single Muv mutants, but no pseudovulvae are formed. In contrast, the double mutant sum-1 ( ar131 ) lin-1 ( n309 )and the triple mutant lin 8( n111 ); lin-9 ( n112 ); sum-1 ( ar131 )are both Muv (the lin-15 ( n309 )and lin-8 ( n111 ); lin-9 ( n112 )phenotype)and Egl- (the sum-1 ( ar131 )phenotype). The double mutant lin-13 ( n387 ); sum-1 ( ar131 )is also Muv, but since lin13 ( n387 )animals are sterile, their egg-laying ability cannot be assessed. One common feature of this latter class of Muv genes ( lin-15 , lin-8 ;1in-9and lin-13 )is that they can all act as Synmuvs under appropriate conditions or with specific alleles.

Our current hypothesis is that sum-1 is involved in some aspect of vulva morphogenesis. This is further supported by the observation of abnormal christmastree structures during vulva morphogenesis in sum-1 mutants. However, somehow the extra vulva cells resulting from mutations in the Synmuv class of Muv genes are different than the extra cells resulting from mutations in the other Muv genes, and this difference can be distinguished by sum-1 .

We are currently trying to clone sum-1 in order to better understand its role in vulva formation. sum-1 maps close to the left of unc-1 on LGX. Using information about the location of polymorphisms flanking unc-1 (kindly provided by Anne Villeneuve) we have rescued sum-1 with the cosmid C08A12 .We are currently testing subclones of this cosmid for rescue.